According to different estimates, between 2,300 and 4,700 people have been killed in police operations or by vigilantes during part of the campaign, as the president introduced a shoot-to-kill policy in the police and urged the population to attack criminals.

On Tuesday, the Philippines police chief, Ronald dela Rosa, expressed disappointment over the failure of the deal with the US, saying that M4 rifles were “reliable.”

The latest outbursts from Duterte came just a few days after he promised to stop swearing, saying that God had ordered him to do so while he was on a plane returning from a visit to Japan.

"While on up there on my way here, I heard a voice telling me to stop swearing or the plane will crash in midair, and so I promised to stop,” he said, according to the Philippine Daily Inquirer.

Since taking office in June last year, Duterte has made plenty of controversial statements about the US, calling President Barack Obama “a son of a whore” and urging America to stop treating the Philippines like “a dog with leash.”

Washington has largely opted to play down the insults to avoid jeopardizing the relationship with a key Southeast Asian ally.